#include <bits/stdc++.h>
using namespace std;
const int mxN = 500001;
int N;
int dp[2*mxN][2][2];
vector<int> A,B;
//dp[i][j][k] = max(#times reach k ending at (i,j))
void calc(int i,int j,int cntA,int cntB){
//cout << cntA << ' ' << cntB << endl;
if(i == 0){
if(j == 0)
cout << 'A';
else
cout << 'B';
return;
}
if(j == 0){
if(A[i-1] <= A[i] && dp[i-1][0][0] >= cntA-1 && dp[i-1][0][1] >= cntB){
calc(i-1,0,cntA-1,cntB);
}
else if(B[i-1] <= A[i] && dp[i-1][1][0] >= cntA-1 && dp[i-1][1][1] >= cntB){
calc(i-1,1,cntA-1,cntB);
}
}
else{//j == 1
if(A[i-1] <= B[i] && dp[i-1][0][0] >= cntA && dp[i-1][0][1] >= cntB-1){
calc(i-1,0,cntA,cntB-1);
}
else if(B[i-1] <= B[i] && dp[i-1][1][0] >= cntA && dp[i-1][1][1] >= cntB-1){
calc(i-1,1,cntA,cntB-1);
}
}
if(j == 0)
cout << 'A';
else
cout << 'B';
}
int main(){
cin >> N;
A.resize(2*N),B.resize(2*N);
memset(dp,0,sizeof(dp));
for(int i=0;i<2*N;i++)
cin >> A[i];
for(int i=0;i<2*N;i++)
cin >> B[i];
dp[0][0][0] = 1;
dp[0][1][1] = 1;
for(int k=0;k<2;k++){
for(int i=1;i<2*N;i++){
for(int j=0;j<2;j++){
if(j == 0){
if(A[i] >= A[i-1])
dp[i][j][k] = max(dp[i][j][k],
dp[i-1][j][k]+(j==k));
if(A[i] >= B[i-1])
dp[i][j][k] = max(dp[i][j][k],
dp[i-1][!j][k]+(j==k));
}
else{
if(B[i] >= A[i-1])
dp[i][j][k] = max(dp[i][j][k],
dp[i-1][!j][k]+(j==k));
if(B[i] >= B[i-1])
dp[i][j][k] = max(dp[i][j][k],
dp[i-1][j][k]+(j==k));
}
}
}
}
if(dp[2*N-1][0][0] >= N && dp[2*N-1][0][1] >= N){
calc(2*N-1,0,N,N);
}
else if(dp[2*N-1][1][0] >= N && dp[2*N-1][1][1] >= N){
calc(2*N-1,1,N,N);
}
else
cout << -1;
cout << endl;
}
